1. Field of the Invention
The present invention relates to an apparatus and method for generating a stereoscopic viewing image from a three-dimensional medical image, and a computer readable recording medium on which is recorded a program for the same.
2. Description of the Related Art
Technologies for performing a stereoscopic display are known.
For example, a stereoscopic display apparatus for a tomographic image in which two parallax images of a cross-section of a test object viewed from left and right eyes are generated based on a plurality of tomographic images obtained by CT or the like and generated parallax images are displayed on two displays is proposed as described, for example, in Japanese Unexamined Patent Publication No. 62 (1987)-016741. Here, the parallax images can be obtained, based on each of left and right viewpoints, by adding up a grey value of each pixel of tomographic images on a visual line connecting between the viewpoint and a projection plane and performing shadowing or coloring as required. When parallax images displayed by the apparatus are observed by an observer with both eyes simultaneously through a stereo viewer, the test object can be observed stereoscopically.
Further, a stereoscopic display method for a virtual endoscopic image is proposed as described, for example, in Japanese Unexamined Patent Publication No. 7 (1995)-210704. More specifically, a parallax image is generated by central projection from each of viewpoints of left and right eyes using a volume rendering method or the like and generated parallax images are displayed on a head mounted display configured such that parallax images for left eye can be viewed only by the left eye and parallax images for right eye can be viewed only by the right eye, whereby the observer can stereoscopically observe a virtual endoscopic image.
Still further, a method in which left and right parallax images representing the ocular fundus of an eye to be examined are obtained and, when a portion of an image stereoscopically displayed using these parallax images is desired to be displayed in an enlarged manner, one of the parallax image is displayed, setting of a desired zoom area in the displayed parallax image is accepted, then an area corresponding to the determined enlarging area is automatically set to the other parallax image, the determined area of each parallax image is cut out, and the area is stereoscopically displayed in an enlarged manner is proposed as described, for example, in U.S. Pat. No. 7,572,009.
The actual visual line for viewing a stereoscopically displayed image differs, in direction, from the visual line of each parallax image. Therefore, if an area is specified for one of the parallax images, as the method described in U.S. Pat. No. 7,572,009, unpleasant sensation may be felt when specifying the area or the determined area may differ from the desired area of the stereoscopically displayed image due to the difference in direction between the actual visual line for viewing the stereoscopically displayed image and the visual line of the parallax image for which the area is specified. Further, in the method described in U.S. Pat. No. 7,572,009, images serving as the basis of stereoscopic display are only two images obtained by imaging, and another image can not be used for the area specification.
Further, in order to perform a stereoscopic display, a display apparatus that supports the stereoscopic display is required. But, in actual clinical practices, not all of the apparatuses for outputting medical images support nor are required to support stereoscopic display.
The present invention has been developed in view of the circumstances described above, and it is an object of the present invention to provide an apparatus and method for generating a stereoscopic viewing image from a three-dimensional medical image capable of responding flexibly and appropriately to the case where stereoscopic output is inappropriate or not required. It is a further object of the present invention to provide a computer readable recording medium on which is recorded a program for causing a computer to perform the method.